90% of the time when a file is in tar format, it is for Linux:
"pLauncher is a front-end (for Linux) to launch emulators with their roms."
You don't need to download pLauncher or anything to play Lunia. I guess your computer just doesn't work with the ijji page. Try the RUNGAME arguement buta suggested. If you ever need to patch it, run Lunia.exe with RUNGAME instead.